Low dimensional nanostructures such as semiconductor nanowires (NW) have recently attracted increasing attention for their potential use as photodetectors in future optical on-chip interconnectors. In particular, germanium (Ge) may be a promising material, due to its CMOS compatibility and exceptional electrical and optical properties. However, the application of Ge NWs as highly sensitive photoconductive elements has been largely overlooked up till now. This work is dedicated to the systematic study of the electro-optical properties of vapor-liquid-solid (VLS) grown Ge NWs. Therefore, monolithic Al-Ge-Al NW heterostructures featuring abrupt interfaces and reliable high-k passivation were established during the course of this thesis. The employed fabrication techniques thereby allowed for the formation of ultrasmall Ge segments without being limited by the alignment of a lithography tool. For such NW systems integrated in back gated field effect transistors, transfer characteristics revealed p-type behavior, which is attributed to trapping effects at the surface. Further, by controlling the charge carrier density through electrostatic gating, a time-dependent change in conductivity over more than 3 orders of magnitude could be observed, with relaxation times in the range of several minutes. To explain this phenomenon, a model was developed in which the slow redistribution of surface charges compensates external electrical fields on the longterm. It was shown that the interplay of electrostatic gating and trap population can cause the charge transport to be electron dominated for several minutes, which was substantiated by the observation of negative differential resistance (NDR) in this regime. Further, low temperature measurements confirmed the proposed kinetic trapping barriers and numerous optical experiments demonstrated dynamic behavior as expected from trapping time constants of surface states in GeOx. Optical experiments were carried out by using a specifically designed measurement setup featuring a spectrally tunable laser source and a lock-in amplifier. Investigations revealed photoconductive gains exceeding 10^7, which is, to the best of my knowledge, the highest ever reported in Ge NWs. In agreement with literature, this was attributed to the photo-enhanced trapping of charge carriers at the surface. Moreover, this high sensitivity remains effective for the whole visible spectral range and for modulation frequencies up to 10 kHz. By systematically reducing channel lengths, ultrasmall photodetectors could be established with feature sizes far below the diffraction limit of incident light.